Rotational piston pump



May 29, 1956 c. o. J. MONTELIUS ROTATIONAL PISTON PUMP Filed Dec. 28, 1951 FIG.

IN V EN TOR.

CARL OSCAR JOSEF MONTELIUS ATTORNEYS United States Patent ROTATIONAL PISTON PUMP Carl Oscar Josef Montelius, Stockholm, Sweden Application December 28, 1951, Serial No. 263,822

6 Claims. (Cl. 103-161) The present invention relates to rotational piston pumps or motors of the type comprising a plurality of pistons slidably disposed in corresponding cylinders in a rotatable cylinder-carrying body and wherein the cylindercarrying body cooperates with a fixed valve member provided with an inlet and an outlet while the movement of the pistons is accomplished by the preferably spherically rounded piston ends engaging the cam surface of a cam member, which is rotatable around a rotational axis.

Such pumps have been made either radial or axial. In the radial pumps the pressures of the pistons act perpendicularly to the rotational axis of the cylinder-carrying body, wherefore the valve member is provided with a cylindrical surface forming the running joint or lit with the cylinder-carrying body. In axial pumps on the other hand where the pistons are disposed parallel to the rotational axis of the cylinder-carrying body, the pressures of the pistons act in the axial direction and the valve member is therefore formed with a flat surface. The slithng movement of the pistons is in both cases produced by a separately journalled rotatable cam member the rotational axis of which either, in the case of radial piunps, extends parallel to but is laterally displaced relative to the rotational axis of the cylinder-carrying body, or, in the case of axial pumps, makes an angle with the last-mentioned axis.

The axial pumps have the great advantage that the fiat surfaces forming the axial running joint between the cylinder-carrying body and the valve member gives a more efiicient and automatically adjustable fiuid tight seal, which effect is not possible to obtain with a cylindrical valve member and a cylinder-carrying body of a corresponding shape. On the other hand, it is usually necessary in axial pumps to connect every piston to the cam member that rotates around an inclined axis by means of cranks provided at both ends with spherical piston heads. This involves an expensive and difficult construction. in radial piston pumps on the other hand it is possible to use with advantage a simple construction such as that wherein the pistons directly engage the surface of the eccentrically rotating cam member in which case the pistons may be pressed against said surface by means of pressure rings.

It is the primary object of the present invention to provide a rotational piston pump wherein the advantages of both of the above-mentioned types of pump are combined without encountering any of the disadvantages.

' It is a further object of the invention to provide'a rotational piston pump in which the piston ends will roll upon their actuating cam surface with a simultaneous oscillatory rotating movement of the pistons around their own longitudinal axis in all operative positions of the pistons so that a sliding movement of the piston ends and the cam surface is prevented.

It is a further object of the invention to provide for continuous engagement of the pistons with the cooperating surface of their actuating cam.

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It is a further object of the invention to provide improved valving and valve port construction in a rotational piston pump.

These and other objects of the invention will be explained below in the following description of an embodiment with reference to the accompanying drawings, wherein Figures 1 and 2 show longitudinal sections taken from different directions and showing the parts in different operative positions while Figure 3 illustrates a detail.

In Fig. 1 the pump is assumed to be set in its zero position while Figure 2 shows the cam member in inclined position with a piston fully drawn out corresponding to said inclined position of the cam member.

The characters 1 and 2 designate two parts forming together an enclosing casing held together by means of bolts (not shown in Figures 1 and 2) while 3 designates a driving shaft. The shaft 3 is supported by the bearing 4 and by a conical or substantially conical fixed valve member 5 disposed at the opposite end of the casing. The valve member 5 is provided with an inlet 6 and an outlet 7 for the fluid to be pumped. The driving shaft 3 is supported at this end by a cylinder-carrying body 9 non-rotatable relatively to the shaft (by reason of axial pins 9a secured in the body and slidable in holes in a flange 9b carried by the shaft) but axially displaceable and acted upon by a coil spring 8 and carrying the pistons 10 which are inserted inclined in corresponding cylinders. The number of pistons 10 is suitably an odd number, only one being shown in the figures for simplicity. Said cylinder-carrying body is formed with a conical recess corresponding to the conical valve member, so that a good sealing effect and a good journalling is obtained between the valve member and the cylinder-carrying body. The cylinder chambers 11 of the pistons communicate with the inlet and the outlet via passages 12 opening into valve ports 13 and 14 (Figures 1 and 3) extending circurnferentially upon the conical valve member 5.

By forming the conical valve member with a suitable apex angle and properly dimensioning the surface area of the valve ports it is possible to balance substantially both the axial and the radial components of the piston pressure such that the cylinder-carrying body is entirely supported by the conical valve plug alone. By virtue of this arrangement no special bearing means for supporting the cylinder-carrying body in the radial direction are required as hitherto proposed for rotational pumps with inclined pistons actuated by cranks.

The outer ends of the pistons are provided with circular heads 15 in cross-section shaped as convex lenses, said heads engaging the cam surface 16 of a cam member 17. Said annular cam member is supported by means of bearing 18 by a ring 19, attached to setting pins 20 rotatably journalled in the casing at right angles to the driving shaft 3. In Figure 2 the cam member is shown set in a desired inclined position. It is to be understood, however, that the present invention may be applied to pumps having a cam member fixedly arranged in a nonadjustable inclined position. The conical cam surface 16, which is shown on the drawing as having a straight generatrix but may be formed with a curved generatrix, makes an acute angle with the rotational axis of the cam member 17. The angle of inclination of the pistons from the driving shaft 3 is in the shown embodiment selected so that in the zero position of the cam member the angle between the longitudinal axis of a piston and the normal to the cam surface at the point of contact with the piston is larger than the maximum angle of inclination used between the cam member and the rotational axes of the cylinder-carrying body, and so that the longitudinal axis of each piston in all operative positions of the .pistonforms an angle with the normal to the cam surface at the point of contact of the cam surface and the piston.

By means of an-arm zlthe'rotational axis of the cam member 17 can be set in the desired angle relatively to the driving shaft 3.

A pressure ring '22 is, by means of a coil spring which in its turn abuts againsta nut ring 24, attached to the cam member 17, held under pressure against the inner surfaces ofthe heads 15 of 'the pistons so that the pistons are maintained in engagement with the cam surface 16. The pressure ring may be dispensed with if the pump fluid is supplied under a 'positive'pressure so great that the pistons-are thereby held in engagement with the cam surface -16.

It will 'be evident that in operation, when the cam surface it t-i'lted as in Figure 2, the rounded piston ends will'roll upon the cam surface with oscillatory rotating movements of the pistons about their own longitudinal axes, while the cam surface itself rotates about its axis within "the bearing 18, minimizing the extent of such oscillato'ry movements.

Above the invention has been described as applied in connection with a pump. It is obvious that an identical arrangement may be used as a motor.

What is "claimed is:

l. A hydraulic device of the type described comprising a rotatable member providing cylinders, pistons slidably disposed in said cylinders, and a cam member roviding a cam surface, said pistons having rounded ends engaging the cam surface, said pistons and cam surface being incIi-ned toward each other and at acute angles relatively to the axis of said rotatable member with the rounded ends of said pistons engaging the cam surface laterally of the longitudinal axes of said pistons in all operative positions =f said cam and said pistons, whereby, during displacement of said pistons in said cylinders, the rounded piston ends will roll upon the cam surface with attendant rotary movements of the pistons about their own longitudinal 'axes.

2. A hydraulic device of the type described comprising a rotatable member providing cylinders, pistons slidably disposed in said cylinders, and a cam member providing a 'cam surface, said pistons having rounded ends shaped as convex lenses engaging the cam surface, said pistons and cam surface being inclined toward each other and at acute angles relatively to the axis of said rotatable memher with the rounded ends of said pistons engaging the cam surface laterally of the longitudinal axes of said pistons in all operative position of said cam and said pistons, whereby, during displacement of said pistons in said cylinders, the rounded piston ends will roll upon the cam surface with attendant rotary movements of the pistons about their own longitudinal axes.

3. A hydraulic device of the type described comprising a rotatable member providing cylinders, pistons slidably disposed in said cylinders, a cam member providing a cam surface, said pistons having rounded ends shaped as convex lenses engaging the cam surface, and a pressure 'ring carried by said cam member and engaging the sides of said convex lenses opposite those in engagement with the cam surface to hold the ends in engagement with the cam surface, said pistons and cam surface being inclined toward each other and at acute angles relatively to the axis of said rotatable member with the rounded ends of said pistons engaging the cam surface laterally of the longitudinal axes of said pistons in all operative positions of said cam and said pistons, whereby, during displacementofsaid pistons in said cylinders, the rounded piston ends will be in constant engagement with the cam surface and will roll upon the cam surface with attendant rotary movements of the pistons about their own longitudinal axis.

4. A hydraulic device of the type described comprising a rotatable member providing cylinders, pistons slidably disposed in said cylinders, an annular cam member providing an internal 'c'onically formed cam surface, said pistons having rounded outer ends shaped as convex lenses engaging the internal cam surface, and a pressure ring-carried by said cam member and engaging the radially outer portions of the inner surfaces 'of said lens shaped piston ends, and spring means urging said pressure ring into engagement with said radially inner surfaces of said lens shaped piston ends to hold the ends in engagement with the cam surface, said pistons and cam surface being inclined toward each other andat acute angles relatively to the axis of said rotatable member with the rounded ends of said pistons engaging the cam surface laterally of the longitudinal axes of said pistons 'in'a ll operative positions of said cam and said pistons, whereby, during displacement of said pistons in said in said cylinders, the rounded piston ends will be in constant engagement with the cam surface and will roll upon the cam surfacewith attendant rotary movements of the pistons about their 'own longitudinal axis.

'5. A hydraulic device of the type described comprising a rotatable member 'p'rovidig cylinders, pistons slidably disposed in said cylinders, and a cam member providing 'a cam surface, said pistons havingrounded ends engaging the can-l surface, said cam member being adjustable and movable to a posit-ion in which displacement of the pistons does not occur during rotation'of said rotatable member, said pistons and cam surface being inclined toward each other and at acute angles relatively to the axis of said rotatable member and, when said cam is in said position in which displacement of said pistons does not occur, the angle between the longitudinal axis of the piston and the normal to the cam surface at the point of contact with the piston end being at least equal to the maximum angle of inclination between the movable cam member and the rotational axis of the rotatable member.

"6. A hydraulicdevic'e of'the type described comprising a rotatable member providing cylinders, pistons slidably disposed in said cylinders and a cam member providing a ca'm'surface, said pistons having rounded ends engaging the 'cam surface, said pistons and cam Surface being infclined toward each other and at acute angles relatively to the axis of said rotatable member, and a conical valve member, said rotatable member having an axially aligned conical recess adapted to receive said conical valve mem- References Cited in the file of this patent UNITED STATES PATENTS 1,970,133 Ferris Aug. 14, 1934 2,069,651 Ferris Feb. 2, 1937 2,273,468 Ferris Feb. 17, 1942 2,420,806 Anderson -s. May 20, 1947 2,455,062 lfield Nov. 30, 1948 2,646,754 Overbeke July 28, 1953 

